DataTables warning: table id=example - Invalid JSON response: How to Debug?

1. Use CTRL+SHIFT+I (or navigate to Current Page Control > Developer > Developer Tools. In the newer versions of Chrome, click the Wrench icon > Tools > Developer Tools.) to enable the Developer Tools.
2. From within the developer tools click on the Network button. 
3. Click the "XHR" sub-button.
4. Initiate an AJAX call.
5. Double click the Name of the page under the Network button. It will open a new page with the details of the error.